1. Field of the Invention
The present invention relates generally to vehicle fuel systems and more particularly to a closed fuel system having a pressurized vessel capable of venting air and/or fuel vapor present in the vessel in a controlled manner.
2. Related Art
Closed (i.e., unvented) fuel systems typically rely on the integrity of the vacuum created and maintained within sealed containers or collapsible bladders to prevent the intrusion of air and/or vapor into the system. Such systems generally do not provide countermeasures to remove internally generated fuel vapor and/or air that enters due to improper fueling or leaks. Accordingly, the total volume of air and/or fuel vapor inside the various components (e.g., fuel bladders, tanks, lines, etc.) of a closed system can reach critical levels capable of progressing through the fuel lines into the engine and thereby inducing engine-seizure.
In contrast, open (i.e., vented) fuel systems typically incorporate a mechanism that allows the removal of undesirable air or fuel-vapor from the fuel lines. Such mechanisms, however, are usually independent from the system fuel sump and are not electronically controlled or modulated based on system conditions. Furthermore, the mechanism may not typically be located immediately before the engine and significant distance between the mechanism and the engine can allow for the intrusion of air through leaks or poorly sealed connections, or additional fuel vapor generated in the lines subsequent to the mechanism, thereby obviating the advantages of an open system.